The management of water represents a wide application area and is receiving considerable attention both due to its limited availability in certain parts of the world as well as to its potential as a source of the spreading of disease as well as of the spreading of unwanted organisms from one region to another. Filtration or more specifically, microfiltration can be considered a preparatory step in treatment processes aiming to improve water quality and to reduce risks associated with water containing unwanted elements. Improved filtration technologies may benefit currently applied treatment methods regardless of media and applications and further open up for the development of improved processes and technologies
Treatment and filtration of ship ballast water is of increasing importance to fleet operators. Transferring large volumes of sea water is known to be damaging to marine biodiversity. The scale of modern ships means the volumes of ballast water tanks is large and consequently the time taken to load and unload ballast tanks is of commercial importance to fleet operators. Additionally, on-board ships space is surprisingly scarce and efficient filtration systems or more specifically micro-filtration systems capable of filtering large volumes of water and removing a considerable amount of matter (organic as well as in-organic) will open up for improved treatment performance and the reduction of the footprint of treatment systems.
The inventors have established that the need for efficient filtration or micro-filtration systems capable of filtering large volumes of fluids such as sea water in small periods of time can be achieved using the invention disclosure herein.
A range of filter systems are available to filter sea water in these applications. Such systems generally comprise a conventional filter element through which the sea water for example flows.
As the liquid flow passes through the wall of the filters elements any dirt, particles or organic matter greater in size than the filter size specification may not pass through the filter element and are trapped on the internal wall of the filter element and begin to form debris, known as a ‘cake’, of filtered matter. As the cake of matter begins to build, the pressure loss over the filter element increases thereby requiring the cake to be cleaned off the interior wall of the filter element if efficiency is to be maintained.
This cleaning process can be achieved by stripping down the filter or through a backwashing mechanism which may be configured for continuous cleaning or triggered only when the pressure loss reaches a certain monitored level or triggered at present intervals or manually. The backwashing mechanism may also make use of a collection chamber underneath the filter elements where the cake of matter from the filter element can be collected and then evacuated by a suitable evacuation pipe.
Various back-washing mechanisms have been employed which allow the filter element to be cleaned through reverse water flow through the filter wall. The back-washing can be performed whilst the filter is in use thus allowing the filter to continuously filter water whilst being cleaned.
The present application describes an unconventional filter arrangement and additionally a back-washing mechanism which advantageously provides a highly efficient filter capable of large volume filtering with minimal pressure drop and process liquid flow.